Emil edwin



E. EDWIN.

ELECTRIC ARC FURNACE. APPLICATION FILED MAY 13. 1915.

Patented Aug. 8, 1916.

EMIL EDWIN, 0F CHRISTIANIA, NORWAY, ASSIGNOR T0 NORSK HYDRO-ELEKTRISKKVAELSTOIEAKTIESELSKAB, OF CHRISTIANIA, NORWAY.

ELno'rRIo-Ano FURNACE.

Specification of Letters Patent.

Patented A11 8, 1916.

Application filed May 13, 1915. Serial No. 27,830.

To all whom it may concern Be it known that I, EMIL EDWIN, a subject ofthe King of Norway, residing at Christiania, Norway, have inventedcertain new and useful Improvements in Electric- Arc Furnaces; and I dohereby declare the following to be a full, clear, and exact descriptionof the invention, such as will enable others skilled in the art to whichit appertains to make and use the same, reference being had to theaccompanying drawings, and to letters or figures of reference markedthereon, which form a part of this specification.

The present invention relates to electric arc furnaces with long stablearcs and particularly to tube furnaces, in which the arc is burningbetween an insulated inner electrode and an outer electrode, which alsomay serve as a cooler.

It is known, that the long stable arcs in electric furnaces of theSchnherr type are generally maintained between an insulated electrodeand a cooled tube, which is electrically connected directly to the flametube and the outer parts of the furnace. Owing to this arrangementit-has previously been considered necessary to connect the said cooleras well as flame tube to earth.

According to this invention the electrode and flame tube have not aconstant potential, which would be the case were the said partsgrounded, so that the potential of these two members may vary inaccordance with the electrical conditions of the system and-as Saidelectrode as well as the flame tube, are arranged so that they canadjust themselves automatically to a potential corresponding to theforces acting on the furnace system and its connections. The importanceof this arrangement is particularly apparent when a. number ofstar-connected furnaces are connected in parallel on a large source ofpower. In the latter case the said arrangement adds materially to thestability of the flame, and as increased stability in most cases meansincreased chemical efficiency, the said arrangement brings with it avery great advantage.

The practical embodiment of the invention is illustrateddiagrammatically on the accompanying drawing.

A, B, C represent three electric flame tube furnaces of the typereferred to. Said furnaces are provided with insulated electrodes D,which are connected to the phases E, F, G of a three-phase system. Theelectric flame is maintained between said electrodes and the interiorwall of the coolers H, which form the opposite end of the tube furnace.Said coolers are electrically con nected with their respective (furnacesand with each other, as indicate by lines I. The furnace tubes and thecoolers are however not connected to earth but are insulated from thesame as well as from any object connected to earth or otherwise liableto prevent the free automatical adjustment of the potential of the starpoint. -The effect of this arrangement "will be understood withreference to the following analogy: If a number of elastic rubberstrings are connected so as to form a star figure, and the free ends ofthe strings each are exposed to varying stresses which strain the sameup to their elastic limit, the several strings will be far more liableto break, if the star center is kept stationary, than if the same isallowed to move freely according to the combined stress transmitted tothe same by the strings. In the analogy the strings correspond to theelectric arcs. which also have a certain elasticlimit, and theconnecting point of the star corresponds to the star point of anelectric star connection. Thevarying mechanical stresses correspond tothe varying electrical forces created in the flame owing toirregularities gin the flow of air around the same If now, compared tothe potential of the eartlr.

as it has previously been done, the star point is made stationary bybeing connected to earth, the several arcs will be liable to break andextinguish (bad stability). If however according to the presentinvention the star point is allowed to adjust itself freely in the fieldof potential, the arcs will be less liable to break and their stabilitywill be increased accordingly.

lVhat I claim is:

l. In a system comprising a plurality of electric arc furnaces, a tubeforming the reaction chamber of each, furnace, an electrode insulated'from the mbe at one end and an electrode electrically connected withthe tube at the other end, a gas inlet near the said insulated electrodeand a gas outlet near the other electrode, an electrical connection to asource of electricity from each of the said insulated electrodes and anelectrical connection insulated from earth between the other electrodes.

In a system comprising a plurality of electric arc furnaces, a tubeforming the reaction chamber of each furnace, an electrode insulatedfrom the tube at one end and an electrode electrically connected withthe tube at theother end, a gas. inlet near the said insulated electrodeand a gas outlet near the other electrode, a polyphase source ofelectricity, an electrical star connection between the said insulatedelectrodes of the furnaces and the source of electricity, and anelectrical connection insulated from earth between the other electrodes.

3. In a system comprising a plurality of electric arc furnaces, a tubeforming the reaction chamber of each furnace, an electrode insulatedfrom the tube at one end and an electrode electrically connected with 2the tube at the other end, a gas inlet near the said insulated electrodeand a gas outlet near the other electrode, a polyphase source ofelectricity, an electrical star connection between the said insulatedelectrodes .belonging to a group of the furnaces and the correspondingphase of the source of electricity, groups of furnaces being connectedin parallel with said source of electricity, and an electricalconnection insulated from earth between the other electrodes.

In testimony that I claim the foregoing as my invention, I have signedmy name in presence of two subscribing Witnesses.

EMIL EDW'IN.

WVitnesses:

M. E. GUTTORNSEN, THS. Hare.

Copies of this patent may be obtained for five cents each, by addressingthe Oommissloner of Patents. Washington, D. G.

